1. Field of the Invention
The present invention relates to a radiographic imaging apparatus that detects radiation as an electric signal. The radiographic imaging apparatus can be used in medical diagnostic equipment or nondestructive testing equipment. The term “radiation” as used herein includes electromagnetic waves, such as alpha rays, beta rays, and gamma rays, as well as X-rays.
2. Description of the Related Art
In general, an X-ray film system that has a fluorescent screen containing an X-ray phosphor layer and is coated on both sides has conventionally been used in X-ray photography. Recently, digital radiographic imaging apparatuses that include an X-ray phosphor layer and a two-dimensional photodetector (sensor panel) have widely been studied, and various patents have been applied for in relation thereto. The digital radiographic imaging apparatuses have advantages in that they have excellent image characteristics, and in that their digital data can be incorporated into a network computer system and can be shared.
In particular, a two-dimensional photodetector (hereinafter referred to as “sensor panel”) that includes an amorphous silicon (a-Si) thin-film semiconductor can be used as not only a photoelectric conversion material, but also a semiconducting material for a thin-film field-effect transistor (hereinafter referred to as “TFT”). Thus, photoelectric conversion elements and TFTs, which serve as switching elements, are conveniently formed at a single time, as proposed in U.S. Pat. No. 5,793,047.
FIG. 6B is a cross-sectional view of a conventional radiographic imaging apparatus. A phosphor layer is formed on a two-dimensional sensor panel composed of a photoelectric conversion element portion in which a plurality of electrical elements, such as photosensors and TFTs, are arranged. Photoelectric conversion elements are placed on a glass substrate 100. Pixels composed of amorphous-silicon photosensors and TFTs (not shown) are arranged in two dimensions on the substrate 100 to form a pixel region 110. The substrate 100 and the pixel region 110 constitute the sensor panel. An electrical connection portion (not shown), which is connected to photosensors or TFTs and is to be connected to an external electrical circuit, is formed on the periphery of the substrate 100. The electrical connection portion is electrically connected and bonded to electrical components 150, such as tape carrier packages (hereinafter referred to as “TCPs”) for driving pixels, using a binding member (not shown), such as an anisotropic conductive film, by heat press bonding. A scintillator 200, which converts X-rays into visible light, is bonded to the substrate 100 with a binder 250, such as an acrylic resin. A supporting member 300 made of a stainless steel plate (cold-rolled stainless steel plate, hereinafter referred to as “SUS”) for supporting the substrate 100 is disposed under the substrate 100. The supporting member 300 is bonded to the substrate 100 with a laminating member 350, for example, made of a two-sided adhesive sheet composed of a binder (for example, a silicon resin binder or an acrylic resin binder) and a foam (for example, a urethane foam or an acrylic foam). These components constitute the radiographic imaging apparatus.
In a manufacturing process or an inspection process of the radiographic imaging apparatus, during an in-process inspection or a screening test after the substrate 100 is fixed on the supporting member 300, if a malfunction or a defect is found in the electrical components 150, such as the TCPs, which are placed on the periphery of the substrate 100 and are connected to the substrate 100, the defective component may be replaced with a new electrical component. In conventional radiographic imaging apparatuses, however, the laminating member 350 under the substrate 100 having the electrical components 150 thereon is soft and therefore uniform bonding between the substrate 100 and the supporting member 300 is hard to achieve at high temperature and high pressure. Thus, the replacement of a defective component is difficult. That is, deformation of the laminating member 350 caused by high temperature and high pressure during bonding causes the electrical connection portion of the substrate 100, which is to be electrically connected to a new electrical component, to deviate from a heater head of a bonding apparatus opposite to the electrical connection portion of the substrate 100. This deviation prevents the heater head from uniformly pressing the electrical connection portion of the substrate 100.